This invention concerns a method to regulate illumination range of a motor vehicle in which signals are measured, or developed, at a position on a front axle and at a position on a rear axle which signals depend upon a relative position of a motor-vehicle body, or chassis, to the front axle and the rear axle, with a difference between these signals being formed as a difference signal, with the resulting difference signal, as a nominal-value signal, being filtered to a first mean, or average, value, with a time for the first average-value formation being determined by a first filter time constant and positions of adjusting elements being regulated when the first filtered, nominal-value, signal deviates from a predetermined, or set, value and an apparatus for performing this method.
A method and an apparatus to regulate the illumination range of a motor vehicle of this general type is known from German Offenlegungschrift DE OS 31 10 094 A1.
Sensors which measure the relative position of a body, or chassis, of a motor vehicle to motor-vehicle axles, or motor-vehicle wheels, are coupled to an analog-multiplexer which feeds the signals from the sensors via an analog/digital-converter to a microprocessor. A filtering of the available signals results in which, in a definite, or set, time period, a mean, or average, value formation of the signals is carried out. For this purpose a number of measured values to be included is set, or predetermined. From the average values then, for each sensor pair corresponding to a front axle sensor and a rear axle sensor, a difference signal is produced corresponding to a headlight adjustment value. Each of these difference signals is fed to a digital/analog converter which is coupled via a respective subsequent operational amplifier with a headlight adjustment apparatus. Depending upon the sense (plus or minus) of the difference signals the adjusting elements are thereby moved forwardly or backwardly and headlight position registers in the microprocessor count upwardly or downwardly. The difference signal must additionally exceed a predetermined threshold value before the headlight adjusting apparatus are operated.
It has proven to be particularly disadvantageous that inclination changes of the motor vehicle body not attributable to changes in a load or road surface unevenness are not recognized and that the regulation upon an appearance of such inclination changes are not altered, whereby false adjustments of the illumination range results so that oncoming traffic is blinded and dangerous situations are brought about. Such an inclination change can for example be conditioned, or caused, by driving about a curve, whereupon, with a filter time constant for average-value formation as is suggested here, a false headlight adjustment for approximately one minute after completion of driving about the curve results because, during the time of driving about the curve, measured values for the average-value formation are used which falsify operating conditions during straight driving.
It has proven to be disadvantageous that with the known apparatus for regulating illumination range of a motor-vehicle four sensors are required to measure a relative position of a body of a motor vehicle to motor-vehicle axles, or motor-vehicle wheels, which sensors are coupled to a microprocessor via an analog-multiplexor because in this manner a cost intensive and expensively constructed apparatus results which, additionally gives rise to high costs upon production and mounting.
It is an object of this invention to provide regulation of an illumination range of a motor vehicle which is uncomplicated and cost effective and which recognizes inclination changes of the motor vehicle body which are not the result of changes of loading or road surface unevenness and which eliminates false adjustments during regulation of the illumination range caused by these of inclination changes.